1. Field of the Invention
The present invention relates to a network system and a method of assigning network addresses to devices in the network system and, more particularly, but not by way of limitation, to a method of automatically assigning unique network addresses to a plurality of electronic appliances of the same kind when the plurality of electronic appliances are first connected to a home network and a home network system therefor.
2. Description of the Related Art
FIG. 1 illustrates an example of a home network system, which will be described below in detail.
The manager of the home network system can control a plurality of electronic appliances connected to a home network N in a centralized way by transmitting control commands to the plurality of electronic appliances and receiving information about the execution results of the control commands through a different appliance such as a PC or a TV.
Such a centralized control scheme requires a home server. The home server is commonly built into an electronic appliance and an electronic appliance with a built-in home server is called a home server appliance. A home server appliance processes control signals sent to and received from a plurality of electronic appliances connected to the home network N (e.g., refrigerators and air conditioners). In addition, the home server appliance assigns a unique network address to an electronic appliance when the appliance is connected to the network for the first time.
The electronic appliances, which are identified on the network by their respective network addresses assigned by the home server appliance, are called client appliances. A client appliance (e.g., C1˜C4 shown in FIG. 1) has a microprocessor for executing a program for home networking and processes data exchanged through the home network N.
In the home network system shown in FIG. 1, the refrigerator acts as the home server and a washing machine C4, a microwave oven C3, etc are connected to the home network as client appliances.
To control a plurality of client appliances through the home network, the home server appliance assigns a unique network address to each of the client appliances when it is connected to the home network N for the first time so that the client appliances can be identified on the network. When receiving a control signal or a control result through the network, the home server appliance detects the source of the signal based on the network address assigned to each of the plurality of client appliances.
FIG. 2 is a flow chart illustrating how a network address is assigned to a client appliance on the home network shown in FIG. 1. When a client appliance hooks up to the home network N first, the client appliance transmits an address assignment request message to the home server appliance (S1). Receiving the address assignment request message, the home server appliance generates a unique network address (S2) and transmits the generated address to the client appliance (S3). Given the network address, the client appliance sets up its network address (S4) and transmits a confirmation message about the address setup to the home server appliance (S5), which completes the network address assignment process.
If a plurality of client appliances of the same kind are connected to the home network N at the same time, the plurality of client appliances transmit their respective address assignment request messages to the home server appliance almost simultaneously. For example, if the power to multiple air conditioners sharing power is turned on as they are physically connected to the home network N, the multiple air conditioners transmit address assignment request messages to the home server appliance almost simultaneously. The source address included in an address assignment request message comprises a product code indicating the product type and a logical address that is commonly set to 0 at factory. Because the air conditioners are of the same kind, they have the same product code and logical address, which means the source addresses included in the address assignment request messages are all identical. As a result, the home server appliance cannot identity the individual sources of the received address assignment request messages.
The home server appliance generates and assigns only one network address to the plurality of client appliances that are indistinguishable on the home network. Consequently, the plurality of client appliances are assigned the same network address and the home server appliance has no means of individually controlling the plurality of client appliances on the home network.
To avoid this problem, the user needs to connect client appliances to the home network one by one so that the home server appliance can generate and assign a unique network address to each of the client appliances. The idea of connecting client appliances individually, however, is a constraint on network management and is not feasible in some cases in which built-in electronic appliances sharing the same power input are used.